Process for making mercaptobenzothiazoles



Patented Oct. 14, 1941 PROCESS FOR MAKING MERCAPTOBENZO- THIAZOLES Claude H. Smith, Tallmadge, Ohio, assignor to Wingfoot Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Application July 23, 1940,

Serial No. 347,001

Claims. (Cl. act-act} This invention relates to a method for making mercaptoarylenethiazoles and more particularly prepared by oxidizing the corresponding 2-mercaptoarylenethiazole. The treatment required is rather specific and the oxidation is of such a character that a high degree of care must be exercised in selecting the oxidizing agents and reaction conditions employed. U. S. Patent 1,880,- 421 describes treating a 2. mercaptoarylthiazole with dilute nitric acid; U. S. Patent 2,024,567 and U. S. Patent 2,024,575 describe the use of hydrogen peroxide; and U. S. Patent 2,043,949 describes the use of ammonium and alkali metal persulfates. Chlorine and certain other oxidizing agents may also be used. There has been no reported observation to indicate that these reactions are reversible to any substantial degree.

' In commercial practice, it has been found that the formation of the di(arylenethiazyl) disulfide may be carried out so that the major portion of the product is obtained in finely dividedform and with a high degree of purity so that it may generally be employed directly as an accelerator of the vulcanization of rubber and for other purposes. However, a small amount of the di(arylenethiazyl) disulfide is often obtained admixed with various impurities so that it is not suitable for direct use. When the di(arylenethiazyl) disulfide is prepared by treating the corresponding Z-mercaptoarylenethiazole with hydrogen peroxide a small portion of the product is almost invariably obtained in the form of hard aggreates of the general size, nature and appearance of sand, which aggregates have been found to consist of the di(arylenethiazyl) disulfide admixed with and bonded together by the corresponding arylenethiazole, sulfur and other impurities. This sandy material is not suitable for use in the compounding of rubber and does not readily lend itself to further refinement and, therefore, in the past it has been a waste material and constituted an economic loss.

According to the present invention, a method has been discovered whereby these hard, sandy aggregates of di(arylenethiazyl) disulfide in admixture with the corresponding arylenethiazole, sulfur and other impurities may be conveniently and economically reclaimed by converting them into the corresponding Z-mercaptoarylenethiazole which itself may be used industrially or which may be reconverted into the di(arylenethiazyl) disulfide.

According to the practice of the invention, the

impure di(aryIenethiaZyDdisuIfide is mixed with materials which react under suitable conditions of temperature and pressure to produce the corresponding 2-mercaptoarylenethiazole in a molten condition and with the production of substantial quantities of by-product hydrogen sulfide. Such methods are illustrated by that described in U. S. 1,631,871 to Kelly, according to which most of the commercial 2-mercaptoarylenethiazoles have been prepared to date. According to the process described in this patent, 2-mercaptobenzothiazole is prepared by reacting aniline with sulfur and carbon bisulfide at a temperatur'e'of about 150-300 C. with the production, theoretically, of one mol of hydrogen sulfide for each mol of 2-mercaptobenzothiazole produced. Other 2-mercaptoarylenethiazoles are prepared by replacing the aniline with other primary aromatic amines having a free ortho position.

According to the present invention, the hard, sandy aggregates of impure di(arylenethiazyl) disulfide may be admixed with the carbon bisulfide, sulfur and primary aromatic amine employed as reactants in the Kelly process and the composite mixture is then treated according to the method described in the Kelly patent. The exact and entire constitution of the impure di- (arylenethiazyl) disulfides is not known with certainty but it has been determined by analysis that they usually contain a major proportion, e. g. about 75%, of the di(arylenethiazyl) disulfide and a minor proportion, e. g. about 25%, of the corresponding arylenethiazole, sulfur and other impurities. The mechanism whereby the di(arylenethiazyl disulfide and the various im- 1 purities are converted into the corresponding 2- zothiazyl disulfide is employed as an example:

The conversion of the arylenethiazole into the droformaldehyde-aniline and sulfur; and U. 5. corresponding 2-mercapto arylenethiazole may Patent -No. 1,865,477 which describes the use of result from the action of the sulfur added as a o, o-diaminodiphenyldisulfide and carbon bisulreactant or that present as an impurity. This fide,

may be represe ted y the f l ow equat n, n 5 While only the preferred embodiments of the w i b th a s p y d s an p invention have been described in detail, it will -;be apparent to those skilled in the art that vari- N\ N\ V oils modifications may be made therein without (2) oH+s ---i c 511" departing from .the spirit of the invention or s S i from the scope of the appended claims.

. What .I claim is:--

Whatever the actual mechanism of the reac- A'meth'od of making z'mercaptoarylenethia zoles which comprises heating a di(arylenetions involved the di(arylenethiazyl) disulfide,

the arylenethiazole and other impurities are-conthlazyl) dlsulfide m cloied at tempera verted into the corresponding 2-mercaptoaryl-;, ture of about 150 to 300 m PresenPe of enethiazole in a substantially complete manner blsulfiqei sulfur and an amme havmg so that, in'large scale production and over a pe-- free Ortho posltlonriod of time, practically all of these materials methoc} of reclalmmg an unPure i i may be recovered-as usable Z-mercaptoaryleneenethmzyl) dlsulfide m compnses adding thiazoles. conversion is of considerable to a mixture of materials which 6910i? under practical importance and makes possible sizable ditions producing z'merca'ptoarylene savings i operatingv costs in View, of the large thiazole in the presence of hydrogen sulfide, re-

volumeeof material handled during the course of I acting mixture t0 prodilce the 2'mercapto' arylenethiazole and recovering the 2-mercaptoa year. v

In practice, the amount of di(arylenethiazyl) arylenethmoledisulfide which it is desired to reconvert into the A method of reclaim-11mg agg'lQmemies of a corresponding ;2 meroaptoarylenethiazole will iiimrylenethiazyl) disulfide Contammg the r ,besmall. Fo example-th impure sandy t sponding arylenethiazole, sulfur andother imrial is only a very small percentageof the disulpurities d prod ced when the correspon m fide formed d, when regularly worked away in mercaptoarylenethiazole is treated with hydrogen succeeding batches, forms only a minor proporperoxide to form the di(arylenethiazyl) disulfide tion of the reactant mass. These small amounts Which p ises adding said agglomerates to a d n t noticeably, influence t course of the mixture of materials which react to produce the ma n tio corresponding 2-mercaptoarylenethiazole in a ln'addition to theprocess described in U. s. molten condition together with ivy-product Patent No. 1,631,871 there are a number of other drogen vsulfide d reactinethe mixture to p processes for preparing 2-mercaptoarylenethiad Said 2-mer0alpiioarylenethiazolezoles which, for the purposes of the present ini A method of reclaiming es Of a vention, may be considered to be full equiva 40 di(arylenethiazyl). disulfide containing the correlents of the Kelly process. In general, these p g arylenethiazole, Sulfur nd er processes employ various possibleintermediate p i and produced when the corresponding roducts of the reaction mixture consisting of 2-mercaptoarylenethiazo1e s t d w h y carbon bisulfide,;sulfur and a primary aromatic gen P e form the di(arylenethiazyl) disulan ine. The reaction conditions employed 'for 45 fi Which Comprises adding d agglomerates 170 each are approximately the same, i. e., they are a mixture of carbon bisulfide, sulfur and an aroin the same range, and each of them produces matic amin having. a free ortho position and. the .2-mercaptoarylenethiazole in a molten condireacting the mixture .to produce a 2mercaptotion and with the formation of substantial quany e e a tities of by-product hydrogen sulfide. Similar 5O 5. A method of reclaiming an impure di(a.ryl results are obtained if the hydrogen sulfide is enethiazyl) disulfide; Containing impurities added as a reactant but it is usually more consubstantially the same character aslthose present venie-nt to take advantage of its formation as a in the sandy agglomerates of impure di(aryleneby-product, Anumber of these related processes thiazyl) disulfide produced when the correspondare'known and they may be illustrated by the inc m r p ryl e hi z le is tr ted with hyprocesses described in U. S. .Patent No. 1,891,198 drogen peroxide to-produce the--di(arylenethiwhich describes the use of dianilino methane, sula yl) disulfide, Whic Comprises ng said imfur and carbon bisulfide; U. s, Patent No, pure di(arylenethiazyl) disulfide to a mixture of 2,070,522 which describes the use of formanilid, materials which react to produc the Correspondsulfur and carbon bisulfide; U. S. Patent No. iilg pt a y1enethiazo1e in a molten Con- 1,858,344 which describes the use of anilinobenzodition together with a Substantial quantity of thiazole and hydrogen sulfide; U. s. Patent No. ivy-Product hydrogen Sulfide and reacting 1,712,968 which describes the use of diphenyl- 1 mixture to produce e said p y e thiourea, carbon bisulfide and sulfur; U. S. Patthlazoleent No; 1,972,963 which describes the use of anhy-' CLAUDE S H- 

